Storage router and method for providing virtual local storage

ABSTRACT

A storage router (56) and storage network (50) provide virtual local storage on remote SCSI storage devices (60, 62, 64) to Fiber Channel devices. A plurality of Fiber Channel devices, such as workstations (58), are connected to a Fiber Channel transport medium (52), and a plurality of SCSI storage devices (60, 62, 64) are connected to a SCSI bus transport medium (54). The storage router (56) interfaces between the Fiber Channel transport medium (52) and the SCSI bus transport medium (54). The storage router (56) maps between the workstations (58) and the SCSI storage devices (60, 62, 64) and implements access controls for storage space on the SCSI storage devices (60, 62, 64). The storage router (56) then allows access from the workstations (58) to the SCSI storage devices (60, 62, 64) using native low level, block protocol in accordance with the mapping and the access controls.

TECHNICAL FIELD OF THE INVENTION

This invention relates in general to network storage devices, and moreparticularly to a storage router and method for providing virtual localstorage on remote SCSI storage devices to Fibre Channel devices.

BACKGROUND OF THE INVENTION

Typical storage transport mediums provide for a relatively small numberof devices to be attached over relatively short distances. One suchtransport medium is a Small Computer System Interface (SCSI) protocol,the structure and operation of which is generally well known as isdescribed, for example, in the SCSI-1, SCSI-2 and SCSI-3 specifications.High speed serial interconnects provide enhanced capability to attach alarge number of high speed devices to a common storage transport mediumover large distances. One such serial interconnect is Fibre Channel, thestructure and operation of which is described, for example, in FibreChannel Physical and Signaling Interface (FC-PH), ANSI X3.230 FibreChannel Arbitrated Loop (FC-AL), and ANSI X3.272 Fibre Channel PrivateLoop Direct Attach (FC-PLDA).

Conventional computing devices, such as computer workstations, generallyaccess storage locally or through network interconnects. Local storagetypically consists of a disk drive, tape drive, CD-ROM drive or otherstorage device contained within, or locally connected to theworkstation. The workstation provides a file system structure, thatincludes security controls, with access to the local storage devicethrough native low level, block protocols. These protocols map directlyto the mechanisms used by the storage device and consist of datarequests without security controls. Network interconnects typicallyprovide access for a large number of computing devices to data storageon a remote network server. The remote network server provides filesystem structure, access control, and other miscellaneous capabilitiesthat include the network interface. Access to data through the networkserver is through network protocols that the server must translate intolow level requests to the storage device. A workstation with access tothe server storage must translate its file system protocols into networkprotocols that are used to communicate with the server. Consequently,from the perspective of a workstation, or other computing device,seeking to access such server data, the access is much slower thanaccess to data on a local storage device.

SUMMARY OF THE INVENTION

In accordance with the present invention, a storage router and methodfor providing virtual local storage on remote SCSI storage devices toFibre Channel devices are disclosed that provide advantages overconventional network storage devices and methods.

According to one aspect of the present invention, a storage router andstorage network provide virtual local storage on remote SCSI storagedevices to Fibre Channel devices. A plurality of Fibre Channel devices,such as workstations, are connected to a Fibre Channel transport medium,and a plurality of SCSI storage devices are connected to a SCSI bustransport medium. The storage router interfaces between the FibreChannel transport medium and the SCSI bus transport medium. The storagerouter maps between the workstations and the SCSI storage devices andimplements access controls for storage space on the SCSI storagedevices. The storage router then allows access from the workstations tothe SCSI storage devices using native low level, block protocol inaccordance with the mapping and the access controls.

According to another aspect of the present invention, virtual localstorage on remote SCSI storage devices is provided to Fibre Channeldevices. A Fibre Channel transport medium and a SCSI bus transportmedium are interfaced with. A configuration is maintained for SCSIstorage devices connected to the SCSI bus transport medium. Theconfiguration maps between Fibre Channel devices and the SCSI storagedevices and implements access controls for storage space on the SCSIstorage devices. Access is then allowed from Fibre Channel initiatordevices to SCSI storage devices using native low level, block protocolin accordance with the configuration.

A technical advantage of the present invention is the ability tocentralize local storage for networked workstations without any cost ofspeed or overhead. Each workstation access its virtual local storage asif it work locally connected. Further, the centralized storage devicescan be located in a significantly remote position even in excess of tenkilometers as defined by Fibre Channel standards.

Another technical advantage of the present invention is the ability tocentrally control and administer storage space for connected userswithout limiting the speed with which the users can access local data.In addition, global access to data, backups, virus scanning andredundancy can be more easily accomplished by centrally located storagedevices.

A further technical advantage of the present invention is providingsupport for SCSI storage devices as local storage for Fibre Channelhosts. In addition, the present invention helps to provide extendedcapabilities for Fibre Channel and for management of storage subsystems.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention and theadvantages thereof may be acquired by referring to the followingdescription taken in conjunction with the accompanying drawings, inwhich like reference numbers indicate like features, and wherein:

FIG. 1 is a block diagram of a conventional network that providesstorage through a network server;

FIG. 2 is a block diagram of one embodiment of a storage network with astorage router that provides global access and routing;

FIG. 3 is a block diagram of one embodiment of a storage network with astorage router that provides virtual local storage;

FIG. 4 is a block diagram of one embodiment of the storage router ofFIG. 3; and

FIG. 5 is a block diagram of one embodiment of data flow within thestorage router of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a block diagram of a conventional network, indicated generallyat 10, that provides access to storage through a network server. Asshown, network 10 includes a plurality of workstations 12 interconnectedwith a network server 14 via a network transport medium 16. Eachworkstation 12 can generally comprise a processor, memory, input/outputdevices, storage devices and a network adapter as well as other commoncomputer components. Network server 14 uses a SCSI bus 18 as a storagetransport medium to interconnect with a plurality of storage devices 20(tape drives, disk drives, etc.). In the embodiment of FIG. 1, networktransport medium 16 is an network connection and storage devices 20comprise hard disk drives, although there are numerous alternatetransport mediums and storage devices.

In network 10, each workstation 12 has access to its local storagedevice as well as network access to data on storage devices 20. Theaccess to a local storage device is typically through native low level,block protocols. On the other hand, access by a workstation 12 tostorage devices 20 requires the participation of network server 14 whichimplements a file system and transfers data to workstations 12 onlythrough high level file system protocols. Only network server 14communicates with storage devices 20 via native low level, blockprotocols. Consequently, the network access by workstations 12 throughnetwork server 14 is slow with respect to their access to local storage.In network 10, it can Also be a logistical problem to centrally manageand administer local data distributed across an organization, includingaccomplishing tasks such as backups, virus scanning and redundancy.

FIG. 2 is a block diagram of one embodiment of a storage network,indicated generally at 30, with a storage router that provides globalaccess and routing. This environment is significantly different fromthat of FIG. 1 in that there is no network server involved. In FIG. 2, aFibre Channel high speed serial transport 32 interconnects a pluralityof workstations 36 and storage devices 38. A SCSI bus storage transportmedium interconnects workstations 40 and storage devices 42. A storagerouter 44 then serves to interconnect these mediums and provide deviceson either medium global, transparent access to devices on the othermedium. Storage router 44 routes requests from initiator devices on onemedium to target devices on the other medium and routes data between thetarget and the initiator. Storage router 44 can allow initiators andtargets to be on either side. In this manner, storage router 44 enhancesthe functionality of Fibre Channel 32 by providing access, for example,to legacy SCSI storage devices on SCSI bus 34. In the embodiment of FIG.2, the operation of storage router 44 can be managed by a managementstation 46 connected to the storage router via a direct serialconnection.

In storage network 30, any workstation 36 or workstation 40 can accessany storage device 38 or storage device 42 through native low level,block protocols, and vice versa. This functionality is enabled bystorage router 44 which routes requests and data as a generic transportbetween Fibre Channel 32 and SCSI bus 34. Storage router 44 uses tablesto map devices from one medium to the other and distributes requests anddata across Fibre Channel 32 and SCSI bus 34 without any security accesscontrols. Although this extension of the high speed serial interconnectprovided by Fibre Channel 32 is beneficial, it is desirable to providesecurity controls in addition to extended access to storage devicesthrough a native low level, block protocol.

FIG. 3 is a block diagram of one embodiment of a storage network,indicated generally at 50, with a storage router that provides virtuallocal storage. Similar to that of FIG. 2, storage network 50 includes aFibre Channel high speed serial interconnect 52 and a SCSI bus 54bridged by a storage router 56. Storage router 56 of FIG. 3 provides fora large number of workstations 58 to be interconnected on a commonstorage transport and to access common storage devices 60, 62 and 64through native low level, block protocols.

According to the present invention, storage router 56 has enhancedfunctionality to implement security controls and routing such that eachworkstation 58 can have access to a specific subset of the overall datastored in storage devices 60, 62 and 64. This specific subset of datahas the appearance and characteristics of local storage and is referredto herein as virtual local storage. Storage router 56 allows theconfiguration and modification of the storage allocated to each attachedworkstation 58 through the use of mapping tables or other mappingtechniques.

As shown in FIG. 3, for example, storage device 60 can be configured toprovide global data 65 which can be accessed by all workstations 58.Storage device 62 can be configured to provide partitioned subsets 66,68, 70 and 72, where each partition is allocated to one of theworkstations 58 (workstations A, B, C and D). These subsets 66, 68, 70and 72 can only be accessed by the associated workstation 58 and appearto the associated workstation 58 as local storage accessed using nativelow level, block protocols. Similarly, storage device 64 can beallocated as storage for the remaining workstation 58 (workstation E).

Storage router 56 combines access control with routing such that eachworkstation 58 has controlled access to only the specified partition ofstorage device 62 which forms virtual local storage for the workstation58. This access control allows security control for the specified datapartitions. Storage router 56 allows this allocation of storage devices60, 62 and 64 to be managed by a management station 76. Managementstation 76 can connect directly to storage router 56 via a directconnection or, alternately, can interface with storage router 56 througheither Fibre Channel 52 or SCSI bus 54. In the latter case, managementstation 76 can be a workstation or other computing device with specialrights such that storage router 56 allows access to mapping tables andshows storage devices 60, 62 and 64 as they exist physically rather thanas they have been allocated.

The environment of FIG. 3 extends the concept of a single workstationhaving locally connected storage devices to a storage network 50 inwhich workstations 58 are provided virtual local storage in a mannertransparent to workstations 58. Storage router 56 provides centralizedcontrol of what each workstation 58 sees as its local drive, as well aswhat data it sees as global data accessible by other workstations 58.Consequently, the storage space considered by the workstation 58 to beits local storage is actually a partition (i.e., logical storagedefinition) of a physically remote storage device 60, 62 or 64 connectedthrough storage router 56. This means that similar requests fromworkstations 58 for access to their local storage devices producedifferent accesses to the storage space on storage devices 60, 62 and64. Further, no access from a workstation 58 is allowed to the virtuallocal storage of another workstation 58.

The collective storage provided by storage devices 60, 62 and 64 canhave blocks allocated by programming means within storage router 56. Toaccomplish this function, storage router 56 can include routing tablesand security controls that define storage allocation for eachworkstation 58. The advantages provided by implementing virtual localstorage in centralized storage devices include the ability to docollective backups and other collective administrative functions moreeasily. This is accomplished without limiting the performance ofworkstations 58 because storage access involves native low level, blockprotocols and does not involve the overhead of high level protocols andfile systems required by network servers.

FIG. 4 is a block diagram of one embodiment of storage router 56 of FIG.3. Storage router 56 can comprise a Fibre Channel controller 80 thatinterfaces with Fibre Channel 52 and a SCSI controller 82 thatinterfaces with SCSI bus 54. A buffer 84 provides memory work space andis connected to both Fibre Channel controller 80 and to SCSI controller82. A supervisor unit 86 is connected to Fibre Channel controller 80,SCSI controller 82 and buffer 84. Supervisor unit 86 comprises amicroprocessor for controlling operation of storage router 56 and tohandle mapping and security access for requests between Fibre Channel 52and SCSI bus 54.

FIG. 5 is a block diagram of one embodiment of data flow within storagerouter 56 of FIG. 4. As shown, data from Fibre Channel 52 is processedby a Fibre Channel (FC) protocol unit 88 and placed in a FIFO queue 90.A direct memory access (DMA) interface 92 then takes data out of FIFOqueue 90 and places it in buffer 84. Supervisor unit 86 processes thedata in buffer 84 as represented by supervisor processing 93. Thisprocessing involves mapping between Fibre Channel 52 and SCSI bus 54 andapplying access controls and routing functions. A DMA interface 94 thenpulls data from buffer 84 and places it into a buffer 96. A SCSIprotocol unit 98 pulls data from buffer 96 and communicates the data onSCSI bus 54. Data flow in the reverse direction, from SCSI bus 54 toFibre Channel 52, is accomplished in a reverse manner.

The storage router of the present invention is a bridge device thatconnects a Fibre Channel link directly to a SCSI bus and enables theexchange of SCSI command set information between application clients onSCSI bus devices and the Fibre Channel links. Further, the storagerouter applies access controls such that virtual local storage can beestablished in remote SCSI storage devices for workstations on the FibreChannel link. In one embodiment, the storage router provides aconnection for Fibre Channel links running the SCSI Fibre ChannelProtocol (FCP) to legacy SCSI devices attached to a SCSI bus. The FibreChannel topology is typically an Arbitrated Loop (FC₋₋ AL).

In part, the storage router enables a migration path to Fibre Channelbased, serial SCSI networks by providing connectivity for legacy SCSIbus devices. The storage router can be attached to a Fibre ChannelArbitrated Loop and a SCSI bus to support a number of SCSI devices.Using configuration settings, the storage router can make the SCSI busdevices available on the Fibre Channel network as FCP logical units.Once the configuration is defined, operation of the storage router istransparent to application clients. In this manner, the storage routercan form an integral part of the migration to new Fibre Channel basednetworks while providing a means to continue using legacy SCSI devices.

In one implementation (not shown), the storage router can be a rackmount or free standing device with an internal power supply. The storagerouter can have a Fibre Channel and SCSI port, and a standard,detachable power cord can be used, the FC connector can be a copper DB9connector, and the SCSI connector can be a 68-pin type. Additionalmodular jacks can be provided for a serial port and a 802.3 10BaseTport, i.e. twisted pair Ethernet, for management access. The SCSI portof the storage router an support SCSI direct and sequential accesstarget devices and can support SCSI initiators, as well. The FibreChannel port can interface to SCSI-3 FCP enabled devices and initiators.

To accomplish its functionality, one implementation of the storagerouter uses: a Fibre Channel interface based on the HEWLETT-PACKARDTACHYON HPFC-5000 controller and a GLM media interface; an Intel 80960RPprocessor, incorporating independent data and program memory spaces, andassociated logic required to implement a stand alone processing system;and a serial port for debug and system configuration. Further, thisimplementation includes a SCSI interface supporting Fast-20 based on theSYMBIOS 53C8xx series SCSI controllers, and an operating system basedupon the WIND RIVERS SYSTEMS VXWORKS or IXWORKS kernel, as determined bydesign. In addition, the storage router includes software as required tocontrol basic functions of the various elements, and to provideappropriate translations between the FC and SCSI protocols.

The storage router has various modes of operation that are possiblebetween FC and SCSI target and initiator combinations. These modes are:FC Initiator to SCSI Target; SCSI Initiator to FC Target; SCSI Initiatorto SCSI Target; and FC Initiator to FC Target. The first two modes canbe supported concurrently in a single storage router device arediscussed briefly below. The third mode can involve two storage routerdevices back to back and can serve primarily as a device to extend thephysical distance beyond that possible via a direct SCSI connection. Thelast mode can be used to carry FC protocols encapsulated on othertransmission technologies (e.g. ATM, SONET), or to act as a bridgebetween two FC loops (e.g. as a two port fabric).

The FC Initiator to SCSI Target mode provides for the basicconfiguration of a server using Fibre Channel to communicate with SCSItargets. This mode requires that a host system have an FC attacheddevice and associated device drivers and software to generate SCSI-3 FCPrequests. This system acts as an initiator using the storage router tocommunicate with SCSI target devices. The SCSI devices supported caninclude SCSI-2 compliant direct or sequential access (disk or tape)devices. The storage router serves to translate command and statusinformation and transfer data between SCSI-3 FCP and SCSI-2, allowingthe use of standard SCSI-2 devices in a Fibre Channel environment.

The SCSI Initiator to FC Target mode provides for the configuration of aserver using SCSI-2 to communicate with Fibre Channel targets. This moderequires that a host system has a SCSI-2 interface and driver softwareto control SCSI-2 target devices. The storage router will connect to theSCSI-2 bus and respond as a target to multiple target IDs. Configurationinformation is required to identify the target IDs to which the bridgewill respond on the SCSI-2 bus. The storage router then translates theSCSI-2 requests to SCSI-3 FCP requests, allowing the use of FC deviceswith a SCSI host system. This will also allow features such as a tapedevice acting as an initiator on the SCSI bus to provide full supportfor this type of SCSI device.

In general, user configuration of the storage router will be needed tosupport various functional modes of operation. Configuration can bemodified, for example, through a serial port or through an Ethernet portvia SNMP (simple network management protocol) or a Telnet session.Specifically, SNMP manageability can be provided via an 802.3 Ethernetinterface. This can provide for configuration changes as well asproviding statistics and error information. Configuration can also beperformed via TELNET or RS-232 interfaces with menu driven commandinterfaces. Configuration information can be stored in a segment offlash memory and can be retained across resets and power off cycles.Password protection can also be provided.

In the first two modes of operation, addressing information is needed tomap from FC addressing to SCSI addressing and vice versa. This can be`hard` configuration data, due to the need for address information to bemaintained across initialization and partial reconfigurations of theFibre Channel address space. In an arbitrated loop configuration, userconfigured addresses will be needed for AL₋₋ PAs in order to insure thatknown addresses are provided between loop reconfigurations.

With respect to addressing, FCP and SCSI 2 systems employ differentmethods of addressing target devices. Additionally, the inclusion of astorage router means that a method of translating device IDs needs to beimplemented. In addition, the storage router can respond to commandswithout passing the commands through to the opposite interface. This canbe implemented to allow all generic FCP and SCSI commands to passthrough the storage router to address attached devices, but allow forconfiguration and diagnostics to be performed directly on the storagerouter through the FC and SCSI interfaces.

Management commands are those intended to be processed by the storagerouter controller directly. This may include diagnostic, mode, and logcommands as well as other vendor-specific commands. These commands canbe received and processed by both the FCP and SCSI interfaces, but arenot typically bridged to the opposite interface. These commands may alsohave side effects on the operation of the storage router, and causeother storage router operations to change or terminate.

A primary method of addressing management commands though the FCP andSCSI interfaces can be through peripheral device type addressing. Forexample, the storage router can respond to all operations addressed tological unit (LUN) zero as a controller device. Commands that thestorage router will support can include INQUIRY as well asvendor-specific management commands. These are to be generallyconsistent with SCC standard commands.

The SCSI bus is capable of establishing bus connections between targets.These targets may internally address logical units. Thus, theprioritized addressing scheme used by SCSI subsystems can be representedas follows: BUS:TARGET:LOGICAL UNIT. The BUS identification is intrinsicin the configuration, as a SCSI initiator is attached to only one bus.Target addressing is handled by bus arbitration from informationprovided to the arbitrating device. Target addresses are assigned toSCSI devices directly, though some means of configuration, such as ahardware jumper, switch setting, or device specific softwareconfiguration. As such, the SCSI protocol provides only logical unitaddressing within the Identify message. Bus and target information isimplied by the established connection.

Fibre Channel devices within a fabric are addressed by a unique portidentifier. This identifier is assigned to a port during certainwell-defined states of the FC protocol. Individual ports are allowed toarbitrate for a known, user defined address. If such an address is notprovided, or if arbitration for a particular user address fails, theport is assigned a unique address by the FC protocol. This address isgenerally not guaranteed to be unique between instances. Variousscenarios exist where the AL-PA of a device will change, either afterpower cycle or loop reconfiguration.

The FC protocol also provides a logical unit address field withincommand structures to provide addressing to devices internal to a port.The FCP₋₋ CMD payload specifies an eight byte LUN field. Subsequentidentification of the exchange between devices is provided by the FQXID(Fully Qualified Exchange ID).

FC ports can be required to have specific addresses assigned. Althoughbasic functionality is not dependent on this, changes in the loopconfiguration could result in disk targets changing identifiers with thepotential risk of data corruption or loss. This configuration can bestraightforward, and can consist of providing the device a loop-uniqueID (AL₋₋ PA) in the range of "01h" to "EFh." Storage routers could beshipped with a default value with the assumption that mostconfigurations will be using single storage routers and no other devicesrequesting the present ID. This would provide a minimum amount ofinitial configuration to the system administrator. Alternately, storagerouters could be defaulted to assume any address so that configurationsrequiring multiple storage routers on a loop would not require that theadministrator assign a unique ID to the additional storage routers.

Address translation is needed where commands are issued in the cases FCInitiator to SCSI Target and SCSI Initiator to FC Target. Targetresponses are qualified by the FQXID and will retain the translationacquired at the beginning of the exchange. This prevents configurationchanges occurring during the course of execution of a command fromcausing data or state information to be inadvertently misdirected.Configuration can be required in cases of SCSI Initiator to FC Target,as discovery may not effectively allow for FCP targets to consistentlybe found. This is due to an FC arbitrated loop supporting addressing ofa larger number of devices than a SCSI bus and the possibility of FCdevices changing their AL-PA due to device insertion or other loopinitialization.

In the direct method, the translation to BUS:TARGET:LUN of the SCSIaddress information will be direct. That is, the values represented inthe FCP LUN field will directly map to the values in effect on the SCSIbus. This provides a clean translation and does not require SCSI busdiscovery. It also allows devices to be dynamically added to the SCSIbus without modifying the address map. It may not allow for completediscovery by FCP initiator devices, as gaps between device addresses mayhalt the discovery process. Legacy SCSI device drivers typically haltdiscovery on a target device at the first unoccupied LUN, and proceed tothe next target. This would lead to some devices not being discovered.However, this allows for hot plugged devices and other changes to theloop addressing.

In the ordered method, ordered translation requires that the storagerouter perform discovery on reset, and collapses the addresses on theSCSI bus to sequential FCP LUN values. Thus, the FCP LUN values 0-N canrepresent N+1 SCSI devices, regardless of SCSI address values, in theorder in which they are isolated during the SCSI discovery process. Thiswould allow the FCP initiator discovery process to identify all mappedSCSI devices without further configuration. This has the limitation thathot-plugged devices will not be identified until the next reset cycle.In this case, the address may also be altered as well.

In addition to addressing, according to the present invention, thestorage router provides configuration and access controls that causecertain requests from FC Initiators to be directed to assigned virtuallocal storage partitioned on SCSI storage devices. For example, the samerequest for LUN 0 (local storage) by two different FC Initiators can bedirected to two separate subsets of storage. The storage router can usetables to map, for each initiator, what storage access is available andwhat partition is being addressed by a particular request. In thismanner, the storage space provided by SCSI storage devices can beallocated to FC initiators to provide virtual local storage as well asto create any other desired configuration for secured access.

Although the present invention has been described in detail, it shouldbe understood that various changes, substitutions, and alterations canbe made hereto without departing from the spirit and scope of theinvention as defined by the appended claims.

What is claimed is:
 1. A storage router for providing virtual localstorage on remote SCSI storage devices to Fibre Channel devices,comprising:a buffer providing memory work space for the storage router;a Fibre Channel controller operable to connect to and interface with aFibre Channel transport medium; a SCSI controller operable to connect toand interface with a SCSI bus transport medium; and a supervisor unitcoupled to the Fibre Channel controller, the SCSI controller and thebuffer, the supervisor unit operable:to maintain a configuration forSCSI storage devices connected to the SCSI bus transport medium thatmaps between Fibre Channel devices and SCSI storage devices and thatimplements access controls for storage space on the SCSI storagedevices; and to process data in the buffer to interface between theFibre Channel controller and the SCSI controller to allow access fromFibre Channel initiator devices to SCSI storage devices using native lowlevel, block protocol in accordance with the configuration.
 2. Thestorage router of claim 1, wherein the configuration maintained by thesupervisor unit includes an allocation of subsets of storage space toassociated Fibre Channel devices, wherein each subset is only accessibleby the associated Fibre Channel device.
 3. The storage router of claim2, wherein the Fibre Channel devices comprise workstations.
 4. Thestorage router of claim 2, wherein the SCSI storage devices comprisehard disk drives.
 5. The storage router of claim 1, wherein the FibreChannel controller comprises:a Fibre Channel (FC) protocol unit operableto connect to the Fibre Channel transport medium; a first-in-first-outqueue coupled to the Fibre Channel protocol unit; and a direct memoryaccess (DMA) interface coupled to the first-in-first-out queue and tothe buffer.
 6. The storage router of claim 1, wherein the SCSIcontroller comprises:a SCSI protocol unit operable to connect to theSCSI bus transport medium; an internal buffer coupled to the SCSIprotocol unit; and a direct memory access (DMA) interface coupled to theinternal buffer and to the buffer of the storage router.
 7. A storagenetwork, comprising:a Fibre Channel transport medium; a SCSI bustransport medium; a plurality of workstations connected to the FibreChannel transport medium; a plurality of SCSI storage devices connectedto the SCSI bus transport medium; and a storage router interfacingbetween the Fibre Channel transport medium and the SCSI bus transportmedium, the storage router providing virtual local storage on the SCSIstorage devices to the workstations and operable:to map between theworkstations and the SCSI storage devices; to implement access controlsfor storage space on the SCSI storage devices; and to allow access fromthe workstations to the SCSI storage devices using native low level,block protocol in accordance with the mapping and access controls. 8.The storage network of claim 7, wherein the access controls include anallocation of subsets of storage space to associated workstations,wherein each subset is only accessible by the associated workstation. 9.The storage network of claim 7, wherein the SCSI storage devicescomprise hard disk drives.
 10. The storage network of claim 7, whereinthe storage router comprises:a buffer providing memory work space forthe storage router; a Fibre Channel controller operable to connect toand interface with a Fibre Channel transport medium, the Fibre Channelcontroller further operable to pull outgoing data from the buffer and toplace incoming data into the buffer; a SCSI controller operable toconnect to and interface with a SCSI bus transport medium, the SCSIcontroller further operable to pull outgoing data from the buffer and toplace incoming data into the buffer; and a supervisor unit coupled tothe Fibre Channel controller, the SCSI controller and the buffer, thesupervisor unit operable:to maintain a configuration for the SCSIstorage devices that maps between Fibre Channel devices and SCSI storagedevices and that implements the access controls for storage space on theSCSI storage devices; and to process data in the buffer to interfacebetween the Fibre Channel controller and the SCSI controller to allowaccess from workstations to SCSI storage devices in accordance with theconfiguration.
 11. A method for providing virtual local storage onremote SCSI storage devices to Fibre Channel devices,comprising:interfacing with a Fibre Channel transport medium;interfacing with a SCSI bus transport medium; maintaining aconfiguration for SCSI storage devices connected to the SCSI bustransport medium that maps between Fibre Channel devices and the SCSIstorage devices and that implements access controls for storage space onthe SCSI storage devices; and allowing access from Fibre Channelinitiator devices to SCSI storage devices using native low level, blockprotocol in accordance with the configuration.
 12. The method of claim11, wherein maintaining the configuration includes allocating subsets ofstorage space to associated Fibre Channel devices, wherein each subsetis only accessible by the associated Fibre Channel device.
 13. Themethod of claim 12, wherein the Fibre Channel devices compriseworkstations.
 14. The method of claim 12, wherein the SCSI storagedevices comprise hard disk drives.